# -*- coding:utf-8 -*-
class Solution:
    def jumpFloorII(self, number):
        # write code here
        f = [0] * (number+1)
        f[0] = 0
        f[1] = 1
        for i in range(2,number+1):
            for j in range(0,i):
                f[i] += f[j]
            f[i]+=1
        return f[-1]

s = Solution()
m = s.jumpFloorII(3)
print(m)